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Article
Publication date: 1 February 2001

K. Dems and Z. Mróz

Damage of a structure affects its stiffness properties and induces a shift in the free frequency spectrum. In the paper, an additional parameter is introduced, such as…

783

Abstract

Damage of a structure affects its stiffness properties and induces a shift in the free frequency spectrum. In the paper, an additional parameter is introduced, such as concentrated elastic or rigid support and mass. The evolution of natural frequencies is analyzed for varying parameter values with respect to damage location. This frequency variation is used in assessing the location and magnitude of damage by introducing the damage indices or by solving the identification problem requiring the minimization of the parameter dependent distance functional. The first part of the paper is concerned with the sensitivity analysis of damage indices with respect to support or mass location. The second part deals with the identification problem for which the specific examples are treated.

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Engineering Computations, vol. 18 no. 1/2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 2 October 2017

Xuepeng Zhan, Jianjun Wu, Mingzhi Wang, Yu Hui, Hongfei Wu, Qi Shang and Ruichao Guo

This paper aims to first apply more advanced anisotropic yield criterions as Yld91 and Yld2004 to spherical indentation simulations, and investigate plastic anisotropy identified…

285

Abstract

Purpose

This paper aims to first apply more advanced anisotropic yield criterions as Yld91 and Yld2004 to spherical indentation simulations, and investigate plastic anisotropy identified from indentation simulations following different yield criterions (Hill48, Yld91, Yld2004) to discover laws. It also aims to compare the difference in plastic anisotropy identified from indentation on three yield criterions and evaluate the applicability of plastic anisotropy.

Design/methodology/approach

This paper uses indentation simulations on different yield criterions to identify plastic anisotropy. First, the trust-region techniques based on the nonlinear least-squares method are used to determine anisotropy coefficients of Yld91 and Yld2004. Then, Yld91 and Yld2004 are implemented into ABAQUS software using user-defined material (UMAT) subroutines with the proposed universal structure. Finally, through considering comprehensively the key factors, the locations of the optimal data acquisition points in indentation simulations on different yield criterions are determined. And, the identified stress–strain curves are compared with experimental data.

Findings

This paper discovers that indentation on Yld2004 is able to fully identify difference in equivalent plastic strain between 0° and 90° directions when indentation depth ht is relatively smaller. And, this research demonstrates conclusively that plastic anisotropy identified from indentation on Yld2004 and Yld91 is more applicable at larger strains than that on Hill48, and that on Yld2004 is more applicable than that on Yld91, overall. In addition, the method on the determination of the locations of the optimal data acquisition points is demonstrated to be also valid for anisotropic material.

Originality/value

This paper first investigates plastic anisotropic properties and laws identified from indentation simulations following more advanced anisotropic yield criterions and provides reference for later research.

Details

Engineering Computations, vol. 34 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 February 2000

A. Dutta and C.V. Ramakrishnan

Design sensitivities of plates and shells under transient dynamic loads with constraints on displacements and stresses are likely to be highly erroneous if proper care is not…

166

Abstract

Design sensitivities of plates and shells under transient dynamic loads with constraints on displacements and stresses are likely to be highly erroneous if proper care is not taken in selecting appropriate finite element mesh and time step size to be used in the analysis. An accurate value of design derivative is assured if an optimal mesh coupled with a reasonably fine time step size is used. The optimal mesh can be obtained iteratively and a number of examples are solved to demonstrate the importance of controlling discretization errors in space and time.

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Engineering Computations, vol. 17 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 13 March 2017

Jun Cao, Zhongwei Yin, Yuqing Cui, Hulin Li, Gengyuan Gao and Xinbo Wang

The purpose of this study was to solve the problem of most woven-fabric self-lubricating bearings that find it difficult to function at temperatures above 320°C, by designing a…

224

Abstract

Purpose

The purpose of this study was to solve the problem of most woven-fabric self-lubricating bearings that find it difficult to function at temperatures above 320°C, by designing a new type of new nuclear joint bearing. The results of this study will help designers to achieve accurate stress distribution, displacement deformation, fatigue life and damage of bearings. All of these can be a guide for designing self-lubricating joint bearings.

Design/methodology/approach

Finite element analysis is undertaken to simulate the new design bearings. To get the most appropriate and accurate results, the room temperature simulation (Simulation A), the modulus of elasticity that changes with temperature (Simulation B) and the thermal-structure-coupled simulation (Simulation C) are compared. The fatigue simulation is conducted to verify whether the self-lubricating method is reasonable and whether the bearing can function for over 60 years in an enclosed environment.

Findings

Stress distribution and displacement deformation of joint bearing can be accurately achieved via the thermal-structure coupled simulation. Work life and damage results have been achieved via the fatigue analysis, and the suggested working loads can be calculated via safety factors.

Originality/value

The newly designed joint bearing in which the graphite is laid on the outside of the inner ring functions and self-lubricates at temperatures above 320°C.

Details

Industrial Lubrication and Tribology, vol. 69 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 January 1992

ZHI‐HUA ZHONG and JAROSLAV MACKERLE

Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years. The finite…

563

Abstract

Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years. The finite element method has been widely used to solve contact problems with various grades of complexity. Great progress has been made on both theoretical studies and engineering applications. This paper reviews some of the main developments in contact theories and finite element solution techniques for static contact problems. Classical and variational formulations of the problem are first given and then finite element solution techniques are reviewed. Available constraint methods, friction laws and contact searching algorithms are also briefly described. At the end of the paper, a bibliography is included, listing about seven hundred papers which are related to static contact problems and have been published in various journals and conference proceedings from 1976.

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Engineering Computations, vol. 9 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 March 1992

C. SAOURIDIS and J. MAZARS

Simple but also accurate models are needed to predict the failure response of concrete structures. Simplicity involves modelling assumptions while accuracy involves objectivity of…

195

Abstract

Simple but also accurate models are needed to predict the failure response of concrete structures. Simplicity involves modelling assumptions while accuracy involves objectivity of both the experimentally identified model parameters and the numerica results. For concrete‐like heterogeneous and brittle materials, the modelling assumptions idealizing the material as a homogeneous continuum with classical linear or non‐linear behaviour, leads to some problems at the identification stage, namely the size effect phenomena. A continuum damage model, representing the non‐linear behaviour due to microcracking, is proposed here for predictive computations of structural responses. A Weibull based theory is used to determine, in a statistical sense, the value of the initial damage threshold. The essential influence of material heterogeneity on the damage evolution, is accounted for with a bi‐scale approach which is based on the idea of the non‐local continuum with local strain. It has already established that the non‐local approaches yield realistic failure predictions and the numerical results are convergent for subsequent mesh refinements. The applications presented here show the ability of the approach to predict the failure response of concrete structures without being obscured by size effect problems.

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Engineering Computations, vol. 9 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 March 1995

D.R.J. Owen, S.Y. Zhao and J.G. Loughran

A finite element solution to the rolling of two‐phase materials ispresented and applied to the rolling of prepared sugar cane. The generalizedBiot theory is extended and modified…

126

Abstract

A finite element solution to the rolling of two‐phase materials is presented and applied to the rolling of prepared sugar cane. The generalized Biot theory is extended and modified to suit the present problem and the velocity of the solid skeleton and the pore pressure are taken as the primary unknowns. The finite element approach is applied to the governing equations for spatial discretization, followed by time domain discretization by standard difference methods. A constitutive relation evaluated from a finite element simulation of experiments performed on a constrained compression test cell is employed. The computational model of the rolling of prepared cane with two rolls is presented. The material parameters of prepared cane are described and their variation during the rolling process are derived and discussed. Numerical results are presented to illustrate the performance and capability of the model and solution procedures.

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Engineering Computations, vol. 12 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 February 1988

Gilles Pijaudier‐Cabot, Zdeněk P. Bažant and Mazen Tabbara

This paper presents a comparison of various models for strain‐softening due to damage such as cracking or void growth, as proposed recently in the literature. Continuum‐based…

318

Abstract

This paper presents a comparison of various models for strain‐softening due to damage such as cracking or void growth, as proposed recently in the literature. Continuum‐based models expressed in terms of softening stress—strain relations, and fracture‐type models expressed in terms of softening stress—displacement relations are distinguished. From one‐dimensional wave propagation calculations, it is shown that strain‐localization into regions of finite size cannot be achieved. The previously well‐documented spurious convergence is obtained with continuum models, while stress—displacement relations cannot model well smeared‐crack situations. Continuum models may, however, be used in general if a localization limiter is implemented. Gradient‐type localization limiters appear to be rather complicated; they require solving higher‐order differential equations of equilibrium with additional bourdary conditions. Non‐local localization limiters, especially the non‐local continuum with local strain, in which only the energy dissipating variables are non‐local, is found to be very effective, and also seems to be physically realistic. This formulation can correctly model the transition between homogeneous damage states and situations in which damage localizes into small regions that can be viewed as cracks. The size effect observed in the experimental and numerical response of specimens in tension or compression is shown to be a consequence of this progressive transition from continuum‐type to fracture‐type formulations.

Details

Engineering Computations, vol. 5 no. 2
Type: Research Article
ISSN: 0264-4401

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Book part
Publication date: 24 February 2023

Micaela Jaramillo-Arévalo, Aldo Alvarez-Risco, Myreya De-La-Cruz-Diaz, Maria de las Mercedes Anderson-Seminario and Shyla Del-Aguila-Arcentales

Science, Technology, Engineering, and Mathematics (STEM) education, its importance, and its difficulties have been defined. This chapter seeks to present the digital tools that…

Abstract

Science, Technology, Engineering, and Mathematics (STEM) education, its importance, and its difficulties have been defined. This chapter seeks to present the digital tools that have been used during the pandemic period and that have been focused on promoting STEM education at different levels. The efforts made by educational organizations worldwide are mentioned. Different regions are shown presenting the best experiences of digital tools that enhance the elements of STEM and can be extended to different levels of education from elementary school to university. On the other hand, successful experiences of the use of technological tools from the teachers' point of view are shown, depicting the tools that have worked the most during the process of adapting to online classes to devise a much better educational plan that continues to take advantage of digital tools for STEM education.

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Sustainable Management in COVID-19 Times
Type: Book
ISBN: 978-1-80382-597-7

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Article
Publication date: 1 February 1992

COLIN THORNTON

Although computer simulated experimentation using the distinct element method (DEM) was originally developed as a tool for examining geomechanical problems, the dynamic nature of…

207

Abstract

Although computer simulated experimentation using the distinct element method (DEM) was originally developed as a tool for examining geomechanical problems, the dynamic nature of the methodology used lends itself more readily to many other areas of scientific and industrial interest. One such area is that of process engineering in which large volumes of particulate materials have to be handled in the context of flow problems (e.g. chutes, hoppers, and pipes). In addition, these particulate materials are often in the form of powders which themselves are agglomerations of much smaller sized particles. Processes such as agglomeration and agglomerate breakdown, either by attrition or comminution, are also amenable to investigation by the DEM.

Details

Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

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